package com.chuan.thinkingjava.think3;

import java.util.HashMap;
import java.util.Map;

public class Test {
	
	public static void main(String[] args) {
		Map<String, String> map = new HashMap<>();
		map.put("1", "2");
		map.put(null, "3");
		String s = "22";
		System.out.println(s.toString());
		System.out.println(map);
	}
}
